1 /*---------------------------------------------------------------------------
3 rpng - simple PNG display program readpng.c
5 ---------------------------------------------------------------------------
7 Copyright (c) 1998-2007 Greg Roelofs. All rights reserved.
9 This software is provided "as is," without warranty of any kind,
10 express or implied. In no event shall the author or contributors
11 be held liable for any damages arising in any way from the use of
14 The contents of this file are DUAL-LICENSED. You may modify and/or
15 redistribute this software according to the terms of one of the
16 following two licenses (at your option):
19 LICENSE 1 ("BSD-like with advertising clause"):
21 Permission is granted to anyone to use this software for any purpose,
22 including commercial applications, and to alter it and redistribute
23 it freely, subject to the following restrictions:
25 1. Redistributions of source code must retain the above copyright
26 notice, disclaimer, and this list of conditions.
27 2. Redistributions in binary form must reproduce the above copyright
28 notice, disclaimer, and this list of conditions in the documenta-
29 tion and/or other materials provided with the distribution.
30 3. All advertising materials mentioning features or use of this
31 software must display the following acknowledgment:
33 This product includes software developed by Greg Roelofs
34 and contributors for the book, "PNG: The Definitive Guide,"
35 published by O'Reilly and Associates.
38 LICENSE 2 (GNU GPL v2 or later):
40 This program is free software; you can redistribute it and/or modify
41 it under the terms of the GNU General Public License as published by
42 the Free Software Foundation; either version 2 of the License, or
43 (at your option) any later version.
45 This program is distributed in the hope that it will be useful,
46 but WITHOUT ANY WARRANTY; without even the implied warranty of
47 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
48 GNU General Public License for more details.
50 You should have received a copy of the GNU General Public License
51 along with this program; if not, write to the Free Software Foundation,
52 Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
54 ---------------------------------------------------------------------------*/
59 #include "png.h" /* libpng header; includes zlib.h */
60 #include "readpng.h" /* typedefs, common macros, public prototypes */
62 /* future versions of libpng will provide this macro: */
64 # define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf)
68 static png_structp png_ptr = NULL;
69 static png_infop info_ptr = NULL;
71 png_uint_32 width, height;
72 int bit_depth, color_type;
73 uch *image_data = NULL;
76 void readpng_version_info(void)
78 fprintf(stderr, " Compiled with libpng %s; using libpng %s.\n",
79 PNG_LIBPNG_VER_STRING, png_libpng_ver);
80 fprintf(stderr, " Compiled with zlib %s; using zlib %s.\n",
81 ZLIB_VERSION, zlib_version);
85 /* return value = 0 for success, 1 for bad sig, 2 for bad IHDR, 4 for no mem */
87 int readpng_init(FILE *infile, ulg *pWidth, ulg *pHeight)
92 /* first do a quick check that the file really is a PNG image; could
93 * have used slightly more general png_sig_cmp() function instead */
95 fread(sig, 1, 8, infile);
96 if (png_sig_cmp(sig, 0, 8))
97 return 1; /* bad signature */
100 /* could pass pointers to user-defined error handlers instead of NULLs: */
102 png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
104 return 4; /* out of memory */
106 info_ptr = png_create_info_struct(png_ptr);
108 png_destroy_read_struct(&png_ptr, NULL, NULL);
109 return 4; /* out of memory */
113 /* we could create a second info struct here (end_info), but it's only
114 * useful if we want to keep pre- and post-IDAT chunk info separated
115 * (mainly for PNG-aware image editors and converters) */
118 /* setjmp() must be called in every function that calls a PNG-reading
121 if (setjmp(png_jmpbuf(png_ptr))) {
122 png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
127 png_init_io(png_ptr, infile);
128 png_set_sig_bytes(png_ptr, 8); /* we already read the 8 signature bytes */
130 png_read_info(png_ptr, info_ptr); /* read all PNG info up to image data */
133 /* alternatively, could make separate calls to png_get_image_width(),
134 * etc., but want bit_depth and color_type for later [don't care about
135 * compression_type and filter_type => NULLs] */
137 png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
143 /* OK, that's all we need for now; return happy */
151 /* returns 0 if succeeds, 1 if fails due to no bKGD chunk, 2 if libpng error;
152 * scales values to 8-bit if necessary */
154 int readpng_get_bgcolor(uch *red, uch *green, uch *blue)
156 png_color_16p pBackground;
159 /* setjmp() must be called in every function that calls a PNG-reading
162 if (setjmp(png_jmpbuf(png_ptr))) {
163 png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
168 if (!png_get_valid(png_ptr, info_ptr, PNG_INFO_bKGD))
171 /* it is not obvious from the libpng documentation, but this function
172 * takes a pointer to a pointer, and it always returns valid red, green
173 * and blue values, regardless of color_type: */
175 png_get_bKGD(png_ptr, info_ptr, &pBackground);
178 /* however, it always returns the raw bKGD data, regardless of any
179 * bit-depth transformations, so check depth and adjust if necessary */
181 if (bit_depth == 16) {
182 *red = pBackground->red >> 8;
183 *green = pBackground->green >> 8;
184 *blue = pBackground->blue >> 8;
185 } else if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) {
187 *red = *green = *blue = pBackground->gray? 255 : 0;
188 else if (bit_depth == 2)
189 *red = *green = *blue = (255/3) * pBackground->gray;
190 else /* bit_depth == 4 */
191 *red = *green = *blue = (255/15) * pBackground->gray;
193 *red = (uch)pBackground->red;
194 *green = (uch)pBackground->green;
195 *blue = (uch)pBackground->blue;
204 /* display_exponent == LUT_exponent * CRT_exponent */
206 uch *readpng_get_image(double display_exponent, int *pChannels, ulg *pRowbytes)
209 png_uint_32 i, rowbytes;
210 png_bytepp row_pointers = NULL;
213 /* setjmp() must be called in every function that calls a PNG-reading
216 if (setjmp(png_jmpbuf(png_ptr))) {
217 png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
222 /* expand palette images to RGB, low-bit-depth grayscale images to 8 bits,
223 * transparency chunks to full alpha channel; strip 16-bit-per-sample
224 * images to 8 bits per sample; and convert grayscale to RGB[A] */
226 if (color_type == PNG_COLOR_TYPE_PALETTE)
227 png_set_expand(png_ptr);
228 if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
229 png_set_expand(png_ptr);
230 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
231 png_set_expand(png_ptr);
233 png_set_strip_16(png_ptr);
234 if (color_type == PNG_COLOR_TYPE_GRAY ||
235 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
236 png_set_gray_to_rgb(png_ptr);
239 /* unlike the example in the libpng documentation, we have *no* idea where
240 * this file may have come from--so if it doesn't have a file gamma, don't
241 * do any correction ("do no harm") */
243 if (png_get_gAMA(png_ptr, info_ptr, &gamma))
244 png_set_gamma(png_ptr, display_exponent, gamma);
247 /* all transformations have been registered; now update info_ptr data,
248 * get rowbytes and channels, and allocate image memory */
250 png_read_update_info(png_ptr, info_ptr);
252 *pRowbytes = rowbytes = png_get_rowbytes(png_ptr, info_ptr);
253 *pChannels = (int)png_get_channels(png_ptr, info_ptr);
255 if ((image_data = (uch *)malloc(rowbytes*height)) == NULL) {
256 png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
259 if ((row_pointers = (png_bytepp)malloc(height*sizeof(png_bytep))) == NULL) {
260 png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
266 Trace((stderr, "readpng_get_image: channels = %d, rowbytes = %ld, height = %ld\n", *pChannels, rowbytes, height));
269 /* set the individual row_pointers to point at the correct offsets */
271 for (i = 0; i < height; ++i)
272 row_pointers[i] = image_data + i*rowbytes;
275 /* now we can go ahead and just read the whole image */
277 png_read_image(png_ptr, row_pointers);
280 /* and we're done! (png_read_end() can be omitted if no processing of
281 * post-IDAT text/time/etc. is desired) */
286 png_read_end(png_ptr, NULL);
292 void readpng_cleanup(int free_image_data)
294 if (free_image_data && image_data) {
299 if (png_ptr && info_ptr) {
300 png_destroy_read_struct(&png_ptr, &info_ptr, NULL);